package com.test.gpa.security.util;

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.JwtBuilder;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;
import java.util.Date;
import java.util.UUID;

/**
 * 生成jwt
 */
public class JwtUtil {
    public static final Long JWT_TTL = 60 * 60 * 1000L;// 60 * 60 *1000 一个小时
    public static final String JWT_KEY = "sangeng";//设置秘钥明文

    public static String getUUID() {
        String token = UUID.randomUUID().toString().replaceAll("-", "");
        return token;
    }


    /*** 生成jwt
     * * @param subject token中要存放的数据（json格式）
     * * @return */
    public static String createJWT(String subject) {
        JwtBuilder builder = getJwtBuilder(subject, null, getUUID());
        return builder.compact();
    }

    /*** 生成jwt
     * * @param subject token中要存放的数据（json格式）
     * * @param ttlMillis token超时时间 * @return */
    public static String createJWT(String subject, Long ttlMillis) {
        JwtBuilder builder = getJwtBuilder(subject, ttlMillis, getUUID());
        return builder.compact();
    }

    private static JwtBuilder getJwtBuilder(String subject, Long ttlMillis, String uuid) {
        SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
        SecretKey secretKey = generalKey();
        long nowMillis = System.currentTimeMillis();
        Date now = new Date(nowMillis);
        if (ttlMillis == null) {
            ttlMillis = JwtUtil.JWT_TTL;
        }
        long expMillis = nowMillis + ttlMillis;
        Date expDate = new Date(expMillis);


        return Jwts.builder().setId(uuid)
                //唯一的ID
                .setSubject(subject)
                // 主题 可以是JSON数据
                .setIssuer("sg")
                // 签发者
                .setIssuedAt(now)
                // 签发时间
                .signWith(signatureAlgorithm, secretKey)
                //使用HS256对称加密算法签 名, 第二个参数为秘钥
                .setExpiration(expDate);
    }

    /**
     * 创建token * @param id
     * * @param subject
     * * @param ttlMillis * @return
     */
    public static String createJWT(String id, String subject, Long ttlMillis) {
        JwtBuilder builder = getJwtBuilder(subject, ttlMillis, id);// 设置过期时间
        return builder.compact();
    }

    public static void main(String[] args) throws Exception {
        String jwt = createJWT("746228272");
        System.out.println(jwt);
        Claims claims = JwtUtil.parseJWT(jwt);
        String userid = claims.getSubject();
        System.out.println(userid);
    }

    /*** 生成加密后的秘钥 secretKey * @return */
    public static SecretKey generalKey() {
        byte[] encodedKey = Base64.getDecoder().decode(JwtUtil.JWT_KEY);
        SecretKey key = new SecretKeySpec(encodedKey, 0, encodedKey.length, "AES");
        return key;
    }

    /*** 解析 ** @param jwt
     * * @return
     * * @throws Exception */
    public static Claims parseJWT(String jwt) throws Exception {
        SecretKey secretKey = generalKey();
        return Jwts.parser().setSigningKey(secretKey).parseClaimsJws(jwt).getBody();
    }


}
